Deck frost heaving

[kdrymer]

Hello I have a small deck (approximately 3.5'X 6') off an enclosed porch and in the winter time the deck seems to suffer from frost heave, which I believe is being caused from the stairs pushing up on the 6x6 post closest to the house. You can see in the pictures that the deck is still lifted up, and the right hand side closest to the house and porch corner seems to be the worst. What are your suggestions to re-leveling it and preventing it from heaving again? The deck is attached to the porch with ledger board, and held up by 6x6 posts on the other side. Thank You!

 

[bud16415]

Sounds like the 6x6 are below the frost line and the 4x4 for the stairs are not.

I built a good size deck a couple years ago and didn’t attach it to the house so the whole thing could float. Where I live we have a 48” frost depth and the last few winters that wasn’t enough. My deck has done fine with allowing it to move.

In your case you need to find out how deep the posts are and if the stair posts are not deep enough you need to correct that.

From your pictures I couldn’t tell what you were showing was the problem with the stairs moving, is it pushing the deck against the house?

I have seen where the steps were not hung off the deck and were free standing and able to move around. That would be one way to fix it.

 

[nealtw]

I have never seen the stairs push a post up like that, usually the stairs just rack a little, but we never install risers either.
I would just cut an inch out to that post, scab over the joint. adjust yearly. If it keeps coming up year after year remove the post and install a concrete pier with a good size footing well below frost line.

 

[kdrymer]

Thanks for both of your thoughts/suggestions. I checked to see how deep the stair posts are and they only appear to be sitting on some type of sill plate (see attached picture). Should the stair posts be placed below the frost line as the main deck posts should be? What would be the best ways of making the stair posts deeper without having to dismantle my deck?

Alternatively if I cut a small part off the main post, do you suggest temporarily supporting the deck and how to go about determining exactly how mud of the post to cut in order for the deck to sit level?

 

[nealtw]

We never set the steps in the dirt. We always go to a concrete slab or sidewalk or even concrete paving squares but they will want to be below the stairs and should be above the surrounding landscape so water does not gather.
If you set a level across the deck in line with the side joist and measure the height you have to raise it so it reads level.

Let's say you have a 2 ft level and you wedge that so it reads level and it is 3/16 up at one end, divide that by 24 and multiply that be the distance between the wall to the far side of the post.
Double check be doing the same exercise from side to side, they should agree if the other post is still in the right place.
Or just find something perfectly straight and longer than that space and lay your level on top- of that and wedge it up to level and measure that.
Might be more accurate if you do this on the bottom of the joists.

 

[kdrymer]

I can't speak for why the deck was built this way as I was not the original owner. Do you suggest attaching the stairs to posts below the first line? I guess it's just hard to determine if that is the real reason the rest of the deck is heaving, or if the deck post itself is lifting up if it's not below the frost line. Not sure how far I should look into this as it's not causing any real issues now and is relatively small.

To address the immediate problem with the deck heaving I will use your level idea with a long piece of 2x4 to determine how much the post is raised on the one side. How do you suggest cutting the post and still supporting the structure? Thanks again for the help!

 

[nealtw]

Near the post lay a chunk of wood on the ground and cut a 2x4 a little long and wedge it between the joist and the chunk on the ground.
I have never seen stairs guilty of damage like this and what you have is what is normal for the bottom of the stairs, I would make sure water is draining away from that area.

 

[KULTULZ]

Both the post and stringer is on the ground...

Neal,

Wouldn't it be better to just bite the bullet, jack and support the stairs and put a proper footing(s) under it?

 

[nealtw]

Both the post and stringer is on the ground...

Neal,

Wouldn't it be better to just bite the bullet, jack and support the stairs and put a proper footing(s) under it?

I have never seen it done, I suspect the post in question is not deep enough.

You put a jack under the the hand rail post, I suspect something would break before you lifted the deck post.

 

[KULTULZ]

I have never seen it done, I suspect the post in question is not deep enough.

You put a jack under the the hand rail post, I suspect something would break before you lifted the deck post.

Yeah, the rear post is already against the siding-

It looks like the stairs would have to be partially disassembled to get footings under the posts.

 

[kdrymer]

Could the ledger board be causing an issue? As I mentioned the heaving is definitely worse on the side closest to the stairs and the soil around that post is usually always damp. It sounds like a new footing may need to be dug, which would require taking apart the stairs. I'll have to weigh the pros and cons of doing this on such a small deck that really isn't utilized that often. I've heard of using strap hinges for fastening the stairs to the deck so that it would allow for the stairs to move slightly without pushing upward on the deck. I may look into doing this.

 

[nealtw]

The hand railing will stop the hinges from working
You could remove that post and run a new 2 ply beam from the far post to the foundation, it would hit the wall just below the siding.

 

[kdrymer]

I snapped a level chalk line accross the outer rim joist and the deck on this side appears to be out of level by 3.25 inches. Would I need to need to cut off that same amount from the post to level it? I believe I would need to cut the notched and non-notched areas. The un-notched area may be difficult to cut as it is against the rim joist, staircase rise and the decking above.

Also with the post being notched on the outer rim joist and the stair case side (riser sitting on it) does this present any issues with putting in a temporary post under the rim joist, from a support perspective?

 

[nealtw]

3 1/2 seems to be a lot. Did you check it both ways, front to back and side to side?
Check the level right in front of the door, if that room was a deck first there might be a slope there too.
You will also have to make room for the bottom of the stairs to go down in the dirt.
I would just make two cuts down below and scab a 2 x 6 on two sides to hold it together when you have it down.

 

[KULTULZ]

...hmmph...

Wonder how good the flashing was done at the ledger board.

IMO, the deck needs to be repaired properly. Anything else is a crap shoot.

Guess there was no permit drawn?

 

[nealtw]

...hmmph...

Wonder how good the flashing was done at the ledger board.

IMO, the deck needs to be repaired properly. Anything else is a crap shoot.

Guess there was no permit drawn?

Flashing should be below the deck board at the wall.
He would be able to see it from under.

This may be temp fix but if left alone the next lift may destroy the deck and if it happens year after year, the post will be much easier to remove.

Even when it is deep enough if the concrete has a mushroom top the frost can grab it.

 

[kdrymer]

Thanks for all the feedback. This particular area stays very damp during a lot of the year, so whatever I decide to do will include improving the drainage around this area. I may get a couple estimates from contractors before deciding to tackle it myself if it's going to involve re-doing footings.